AR Sponsor
Posted: 10/19/2007 7:43:55 AM EDT
|
Hi, I am a new member here adjust purchased a Bushmaster Predator. So Far I love the riffle! I have a question though. I have put about 140 rounds of factory ammo through it, consisting of mostly Black Hills and Remington. It has functioned flawlessly. I had not cleaned it yet as I had a few variations of hand loads that I wanted to try as well at the range. I noticed that when I switched to my hand loads that it stopped cycling correctly. The riffle would fire and eject the case but would not feed a new cartridge as the bolt closed. After each shot was ejected I had to cycle the bolt manually to get it to load the next round. Also when the last shot was fired and the magazine was empty the bolt was not staying open like it did with the factory ammo. As for the hand loads they were 52 and 69 gr Sierra BTHP bullets with 18.3 - 21gr of IMR 4198 powder. I have cleaned the riffle thoroughly and was wondering what may be causing this problem? Thanks for any info as it is greatly appreciated. Joe |
|
Dang it I keep hitting the report button instead of reply....... anyway I bought a brand new Bushy a little while back and started having an identical problem, but with factory ammo. The first several cycled fine and then started to have the same problem you are, turned into a single shot. The conclusion we came to was a gas tube problem. Since I bought it brand new I took it back and got a new rifle and have not had any problems since. The new one has not had any problems at all. This is my third Bushy AR and was the first time I had any problem with them. Good luck. |
My guess would be that your hand loads were underpowered and the rifle was short stroking. |
|
21gr sounds a little light w/ 52gr bullets.......I have seen published data at 22.5 with 4198 and 52's. Bump it up a little. RL15 or Varget are a better powder for the 69's..... 25gr seem to work well in either powder. Personaly, I use 27gr of WCC844 behind any 50 - 55gr bullet. Hits almost 3200 out of a 20" barrel with good accuracy. |
+1 Try firing the BH or Rem ammo again and see if it functions normally. If it does, it most likely your hand loads are under powered. |
I disagree, 21.0 Gr of IMR 4198 is the max load if not very close with 52 gr. bullets. Personally I would try a different powder such as WW748 or Varget. |
I may not be a reloader (yet), but the rifle is obviously short stroking. There is not enough gas to get the bolt all the way back, which is why it's not stripping rounds from the mag or going far enough back for the bolt catch to work on last round. He's trying out new handloads, and these are what is not working. He said that it has worked fine with factory ammo previously. To me it says, "underpowered ammo not gassing rifle enough." |
| 4198 is a relatively fast burning powder compared to most other AR powders. I was using that powder when I started reloading and had no problems in my 16" middy, but my 20" Ar would do the same thing, wouldnt hold open on last round firing. If you look it up youll see others have the same issue. Find a faster burning powder, dont even try to increase the powder weight with 4198, it is a very accurate powder, but burns way too fast. Switched to w748 and it all worked out and is just as accurate. |
Just like the rings on a piston. The gaps should be at 120* angles from each other optimally. For common folks like you and me, just make sure they arent all lined up, thats all. Otherwise...just like in a motor, you get "blowby" and performance is reduced. |
AR Sponsor